1. Field of the Invention
The present invention relates to apparatus for automatically placing valve bags onto a filler spout to be filled thereby. More specifically, the present invention relates to an automatic suspension for placing valve equipped bags upon the spout of a filling apparatus through which the bags may be filled with flowable particulate material.
Valve bags are of the type that comprise a top which is open at one end so as to be able to receive the filling spout of a filling machine. The principal advantage of such bags is that they close automatically when filled and removed from the machine so that no special sealing procedures are needed to close the bags at their top subsequent to their being filled.
2. Prior Art
Because of the manifest disadvantages of manually placing the open valve end of one bag at a time on the filling spout of a filling machine, a substantial prior art has developed disclosing a plurality of sequentially controlled apparatus for performing the indicated valve bag placement operation automatically. By way of example, the following table lists a number of issued patents disclosing apparatus of the type indicated:
TABLE I ______________________________________ U.S. Pat. No. Inventor ______________________________________ 2,548,075 Stoker 2,828,596 Dowty et al 3,053,027 Frost 3,213,588 Peterson 3,225,515 Inglett 3,287,879 Miller 3,312,038 Knauf 3,423,903 Miller 3,462,917 Nakashima 3,466,837 Sturges 3,522,691 Adcox 3,691,715 Kelly et al 3,715,858 Durant et al 3,785,414 Obara 3,884,278 Nakashima 3,986,322 Taylor 3,989,073 Remmert 4,019,546 Hastrup 4,128,116 Uthoff et al ______________________________________
Unfortunately, each of the prior art patents listed in Table I discloses an apparatus which suffers from one or more disadvantages that renders it less desirable in some aspect of its operation. For example, the aforementioned prior art devices may have proved satisfactory in handling only valve bags of the type comprising heavy multi-ply paper, which bags inherently have a substantial degree of structural stiffness that renders them relatively easy to stack and manipulate. However, none of such devices known to applicant is capable of satisfactorily handling valve bags of the type made of lightweight plastic. Such plastic valve type bags are highly advantageous because of their lower cost, lighter weight and increased resistance to contamination by moisture or leaks of the contained particulate matter. However, until applicant's present invention, such plastic bags have constituted a problem for the manufacturers of bag placer apparatus because of the inherently increased difficulty of handling such highly flexible plastic materials. The tendency of plastic valve bags to flex in their centers renders such bags especially difficult to stack in a vertical pile without the centers thereof forming a concave shape, the curvature of which increases in proportion to the number of bags in the stack. Furthermore, many prior art devices for automatically applying valve bags to filler spouts, require that the bags be placed in a horizontal stack in which their weight is supported substantially along one edge. This is perfectly acceptable for the stiff conventional paper bags referred to above, but plastic valve bags do not have the structural rigidity to permit support of the valve bag weight on one edge with the bag in a substantially flat vertical plane. As a result, plastic valve bags are simply not acceptable in any prior art bag placer apparatus that utilizes horizontally directed stacks of bags, and are of at least highly questionable applicability even in apparatus using vertical stacks of bags.
Thus, the inability of prior art devices known to applicant to handle the more modern, lighter weight and less costly plastic valve bags, is a highly significant disadvantage which renders all such prior art devices substantially obsolete and inappropriate for their intended purpose in conjunction with plastic valve bags.
Another substantial disadvantage of prior art valve bag placing apparatus is that although manual labor is not required to place the bag on the filling spout, a certain amount of time-consuming care must be utilized to stack the bags within very limited position tolerances so that the individual bags in such stacks will be appropriately placed to be received by the prior art apparatus for automatic placement on the filling spout. As a result of the special additional care that must be utilized in forming the stack, a portion of the cost and time-saving advantage provided by the automatic apparatus is lost.
Still a further disadvantage of prior art automatic apparatus for placing valve bags is the reliability of the mechanism used in such apparatus for opening the valve end of the bag as required to ensure positive placement of the open valve portion on the filler spout. Such reliability is needed to prevent particulate material from being poured onto the ground or otherwise poured outside the bag, and so that only a trivial number of bags are inadvertently caused to miss the spout and fall empty on the floor or conveyor belt below the filling spout.